Yolk stalk
A narrow tube present in the early embryo that connects the midgut of the embryo to the yolk sac outside the embryo through the umbilical opening.
Later in development, the yolk stalk is usually obliterated, but a remnant of it may persist: most commonly as a finger-like protrusion from the small intestine known as Meckelis diverticulum.
Found in 2 to 4 percent of people, Meckelis diverticulum may become inflamed (much like the appendix) and require surgical removal.
Also known as the omphalomesenteric duct, umbilical duct, or vitelline duct